linux-kernel - Re: [PATCH 1/3] ring-buffer: Add uname to match criteria for persistent ring buffer

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Message-ID: <CAADnVQLwP6DsPCTu-xQ_q7S5ismAM_XvVOfG_EUSVQAqh64VzQ@mail.gmail.com>
Date: Tue, 17 Dec 2024 17:53:19 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Florent Revest <revest@...gle.com>, Daniel Borkmann <daniel@...earbox.net>, bpf <bpf@...r.kernel.org>, 
	Steven Rostedt <rostedt@...dmis.org>, Alexei Starovoitov <ast@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	linux-trace-kernel <linux-trace-kernel@...r.kernel.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, stable <stable@...r.kernel.org>
Subject: Re: [PATCH 1/3] ring-buffer: Add uname to match criteria for
 persistent ring buffer

On Tue, Dec 17, 2024 at 5:39 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Tue, 17 Dec 2024 at 17:26, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > Let me go separate that part out and maybe people can point out where
> > I've done something silly.
>
> Ok, that part I had actually already locally separated out better than
> some of my later patches in the series, so I sent it out as
>
>   https://lore.kernel.org/all/20241218013620.1679088-1-torvalds@linux-foundation.org/

lgtm.
Since bstr_printf() converts 1/2/4 to unsigned long long num
with a sign according to the format specifier it's good
from the calling convention perspective.
Doesn't matter here, but anyone passing 32-bit ints around
needs to be aware of odd riscv abi promotion rules.
x86-64 and arm64 zero extend 32-bit ints while riscv does sign
extension when s32 and u32 are passed.
Quote from the spec:
"In RV64, 32-bit types, such as int, are stored in integer registers
as proper sign extensions of their 32-bit values; that is, bits 63..31
are all equal. This restriction holds even for unsigned 32-bit types."